CRETACEOUS PERIOD

The Mesozoic era ended with the cretaceous period, which lasted from 146 to 65 million years ago. During this period, Gondwanaland and Laurasia were breaking up into smaller land masses that more closely resembled those of the modern continents. the climate remained mild and moist but the seasons becomes more marked. Flowering plants, including deciduous trees, replaced many cycads, seed ferns and conifers. Animal species become more varied, with the evolution of new mammals, insects, fish, crustaceans and turtles. Dinosaurs  evolved into a wide variety of species during Cretaceous times; more than half of all known dinosaurs including Iguanodon, Deinonychus, Tyrannosaurus and Hypsilophodon lived during this period. At the end of the Cretaceous period, however dinosaurs become extinct. The reason for this mass extinction is unknown but it is thought to have been caused by claimatic changes due to either a catastropic meteor impact with the Earth or extensive volcanic eruptions.